The present invention relates to a method and a system of detecting vehicle speed limiting system tampering utilizing global positioning system data commercial vehicles including trucks and buses may be part of a fleet of vehicles that are owned and operated by a fleet owner.
Fleet owners faced with increasing fuel costs and drivers who exceed speed limits need a simple and reliable system for limiting vehicle speed that cannot be easily defeated by drivers or mechanics. Mechanical or electronic speed governors have been developed to automatically limit a vehicle""s operating speed. Governors and other speed limiting devices may be defeated or disconnected by a driver. When this occurs fleet owners suffer losses as a result of excessive fuel costs and lose the ability to control the operation of trucks by limiting their speed.
One example of a speed limiting system used to detect tampering with a vehicle speed sensor is disclosed in U.S. Pat. No. 5,896,083 and is assigned to the assignee of this application. The ""083 patent compares a gear ratio set to a reference gear ratio to determine a gear ratio difference value. An error signal is generated to indicate tampering with the vehicle speed sensor when the gear ratio difference value exceeds a threshold value. While this approach has proven to be generally effective, a more flexible and universal approach is needed to determine if there has been any tampering with a vehicle speed limiting system.
Global positioning systems have been developed to aid in navigation. Global positioning systems utilize a plurality of satellite signals that are integrated to provide an accurate indication of the position of the global positioning system receiver. Global positioning systems usually provide information that is either provided as a digital readout or is used to display the location in conjunction with a map display.
The use of a global positioning system to calibrate a vehicle""s speed sensor is disclosed in U.S. Pat. No. 5,828,585. This patent claims a system and method of automatically calibrating a vehicle speed sensor signal to provide an accurate speed signal for use in vehicle navigation systems. This patent fails to disclose the use of a global positioning system in a method or a system for detecting tampering with a vehicle speed limiting system.
These and other problems and limitations inherent in prior art methods and systems are addressed by applicant""s invention as summarized below.
According to the present invention, an engine control module (ECM) obtains vehicle position data from a global positioning system (GPS) at spaced time intervals and calculates the average road speed over the time interval. The average road speed is then compared to a value for the allowed vehicle road speed. If the average road speed is in excess of the allowable road speed, tampering with the vehicle speed sensor is signaled. Once tampering is detected the ECM may log the signal memory, reduce the allowable road speed of the vehicle or reduce the allowable engine RPM. The system also determines whether the GPS was tampered with, for example by disconnecting its wires and may either note the tampering or limit road speed or engine RPM in response to the tampering detected.
According to the present invention a method of detecting vehicle speed sensor tampering for a vehicle having a global positioning system (GPS), a clock, and an engine control module (ECM). The method comprises storing a first position signal from the GPS and storing a first time value substantially simultaneously while storing the first position signal. After a period of time, a second position signal from the GPS is stored substantially simultaneously with a second time value. The term substantially simultaneous as used herein means that the GPS system position reading and time value are coordinated to permit an accurate average speed value based upon the readings. The average vehicle speed is then calculated over the period of time and is compared to a stored value of a maximum vehicle speed. A vehicle speed limiting system tampering signal is then generated if the average vehicle speed is greater than the maximum vehicle speed. The ECM is controlled in response to the vehicle speed limiting system tampering signal.
The ECM may be controlled by changing or limiting the allowed engine revolutions per minute or by changing or limiting the allowed vehicle road speed. The ECM may also be controlled to record data in a data recorder to provide a record that vehicle speed limiting system tampering signal was generated by the system.
If the average vehicle speed is not greater than the maximum vehicle speed and this method may include the step of checking the operation of the GPS to determine if the GPS was tampered with or disabled. If so, the system would generate a vehicle speed limiting system tampering signal.
The present invention also relates to a system for detecting vehicle speed sensor tampering. The system includes an engine control module, a global positioning receiver operatively connected to the engine control module and a clock operatively connected to the engine control module. The engine control module learns a first position from the global positioning receiver and first time from the clock. The system waits a predetermined period of time and the engine control module learns a second position from the global positioning receiver and a second time from the clock. The engine control module calculates the average vehicle speed that is compared to a predetermined value corresponding to a speed limit value stored in the engine control module. If the average vehicle speed is greater than the speed limit value, a signal is generated to cause the engine control module to limit the engine speed in response to the signal being generated.
According to the system, the engine speed may be limited by limiting the allowed number of engine revolutions per minute, limiting the allowed vehicle road speed or by making a record in a data recorder.
The system also checks the operation of the global positioning system to determine if the global positioning system was tampered with or disabled whereupon the system may generate a signal indicating that there has been tampering with the global positioning system.
The above objects and advantages and other features of the invention are better understood in view of the attached drawing and following detailed description of the method and system of the present invention.